It is already known to provide attachments of the above-noted type for a wheel-chair. For instance, reference is had to U.S. Pat. No. 3,485,510, dated Dec. 23, 1979 and entitled: "Self-PROPELLING AND STEERING ATTACHMENT APPARATUS FOR A WHEELCHAIR".
Known attachments either require considerable modification of the conventional wheel-chair or removal of the user from the wheel-chair prior to the installation of the attachment.